Impact of the Rare Earth Element La on the Microstructure and Mechanical Properties of the Al/Steel Bimetallic Composite Interface Fabricated by Liquid–Solid Casting

This research aimed to explore the influence of the rare-earth element La on the interface microstructure and mechanical properties of Al/steel bimetallic composites produced through liquid–solid casting. The addition of the rare earth element La refined the morphology of eutectic silicon and ensured its uniform and continuous distribution. The interface structure of the Al/steel bimetallic composite exhibited distinct layering, primarily comprising two layers. The first layer, termed reaction layer I, comprised Al₅Fe₂ and τ₁-Al₂Fe₃Si₃ phases. While the second layer, termed reaction layer II, consisted of Al₁₃Fe₄, τ₅-Al₇Fe₂Si, and τ₆-Al₉Fe₂Si₂ phases. The addition of La did not alter the types of intermetallic compounds present in the Al/steel reaction layer. As the La content increased to 0.3%, there was a notable reduction in the average thickness of both reaction layers I and II, reaching a minimum. The presence of La effectively restrained the growth of intermetallic compounds within the reaction layer. Consequently, the shear strength of the Al/steel bimetallic sample exhibited an initial increase followed by a subsequent decrease with increasing La content. With the addition of 0.3% La, the shear strength of the sample peaked at 30.1 MPa, representing a 66% increase.

Graphical Abstract